Person wrecking web programme has raised regret after it (8)
I believe the answer is:
saboteur
'person' is the definition.
(saboteur is a kind of person)
'raised regret after it' is the wordplay.
'raised' says the letters should be written backwards (going up in a down clue).
'regret' becomes 'rue' (to rue something is to regret it).
'after' is a charade indicator (letters next to each other).
'it' becomes 'sabot' (I can't justify this - if you can you should give a lot more credence to this answer).
'rue' back-to-front is 'eur'.
'eur' after 'sabot' is 'SABOTEUR'.
'wrecking web programme has' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for saboteur that I've seen before include "Rue boast about one who inflicts deliberate damage" , "One who causes deliberate damage to plants or machinery" , "Hacker possibly" , "One who disrupts or damages by design" , "One engaged in malicious disruption" .)